5-Amino isoxazole from 3-amino acrylonitrile

ABSTRACT

A process for preparing 5-aminoisoxazole by reacting an 3disubstituted-aminoacrylonitrile and an acid addition salt of hydroxylamine.

I Unite States 1.1mm [1 1 Leimgruher et a1.

1 Nov. 4, 1975 S-AMINO ISOXAZOLE FROM 3-AMINO ACRYLONITRIILE Inventors: Willy Leimgruber, Montclair;

Manfred Weigele, North Caldwell,

both of NJ.

Assignee: Hoffmann-La Roche llnc., Nutley,

Filed: Jan. 23, 1974 Appl. No.: 435,918

Related US. Application Data Division of Ser. No. 262,880, June 14, 1972, Pat. No. 3,810,935, which is a division of Ser. No. 42,545, June 1, 1970, Pat. No. 3,709,922.

US. Cl 260/307 18 Int. C13. C07D 261/14 Field of Search 260/307 H Primary ExaminerRaym0nd V. Rush Attorney, Agent, or Firm-Samuel L. Welt; Jon S. Saxe; William H. Epstein [57] ABSTRACT A process for preparing S-aminoisoxazole by reacting an 3-disubstituted-aminoacrylonitrile and an acid addition salt of hydroxylamine.

2 Claims, N0 Drawings s MiNo isoxAzoLErRoM s amrno ACRYLONIITRILE CROSS REFERENCE TO RELATED APPLICATIONS This application is a divisional application of Ser. No. 262,880, filed June 14, 1972 now U.S. Pat. No.

3,810,935, May 14, 1974, which in turn is a divisional application of Ser. No. 42,545, filed June l, 1970, now US. Pat. No. 3,709,922, Jan. 9, 1973.

BACKGROUND OF THE INVENTION to synthesize both malononitrile and cyanoacetamide from inexpensive and readily available starting materials.

SUMMARY OF THE INVENTION In accordance with this invention, it has been found that cyanoacetamide which has the formula:

can be simply and economically synthesized from a compound of the formula:

wherein R and R are lower alkyl.

Furthermore, this invention provides a simple and direct means for producing malononitrile which has the formula:

directly from the compound of formula II above.

The compound of formula II can be easily synthesized from readily available and commercially economical materials by two methods. In the first method of producing the compound of formula II above, an acetal of the formula:

wherein R and R are as above; and R is lower alkyl;

2 is condensed at a temperature of at least C. with acetonitrile. In accordance with the second method of producing the compound of formula II above, a compound of the formula:

wherein R and R are as above;

is treated with a hydrogen acceptor at a temperature of at least 50C. in the presence of a dehydrogenation cat alyst.

DETAILED DESCRIPTION As used throughout the specification, the term lower alkyl includes both straight and branched chain alkyl groups containing from I to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, and the like. As used throughout the specification, the term lower alkanoyl" includes alkanoyl groups containing from 2 to 6 carbon atoms such as acetyl, propionyl and buty ryl. The term alkali metal includes such metals as sodium potassium and lithium.

The reaction of acetonitrile with the acetal of formula IV to form the compound of formula II is carried out at a temperature of at least 80C. Generally, it is preferred to utilize a temperature of from C, to 250C. in carrying out this reaction. While this reaction can be carried out at atmospheric pressure, superatmospheric pressures are utilized when higher temperatures are utilized. This reaction can be carried out with out the need for utilizing any solvent. However, if de sired, an inert organic solvent can be utilized. Any conventional inert organic solvent such as benzene, toluene, methylene chloride, can, if desired, be utilized in carrying out this reaction.

The second method of preparing the compound of formula II above is by treating a compound of formula V above with a hydrogen acceptor at a temperature of at least 50C. in the presence of a dehydrogenation catalyst. Any conventional dehydrogenation catalyst can be utilized in carrying out this reaction. Among the preferred dehydrogenation catalysts which can be utilized in this reaction are palladium, Raney nickel and cupric chromite. In carrying out this reaction, any conventional hydrogen acceptor can be utilized. Among the preferred hydrogen acceptors is oxygen which can be supplied by carrying out the reaction in the presence of which can be advantageously utilized in this process are aliphatic ethers containing at least one ethylenic moiety bound to the oxygen atom and having from 3 to 15 carbon atoms such as methyl vinyl ether and cyclic ethers such as dihydropyran.

In converting the compound of formula V above to the compound of formula II above, no solvent need be present. Generally, in carrying out this reaction, a temperature of at least 50C. should be utilized with temperatures of between 80C. to 200C, being preferred. If high temperatures are utilized, the reaction may be carried out under superatmospheric pressure.

In accordance with this invention, the compound of formula I above is synthesized from the compound of formula II above by means of the following reaction scheme:

wherein R and R are as above.

The compound of formula II above is converted to the compound of formula VI above, via reaction step (a), by reacting the compound of the formula II above with an acid addition salt of hydroxylamine. Any conventional acid addition salt of hydroxylamine can be utilized in carrying out this reaction. Among the conventional acid addition salts of hydroxylamine which can be utilized in carrying out this reaction are the hydrohalic acid addition salts, and the sulfuric acid addition salts of hydroxylamine. The preferred acid addition salts of hydroxylamine are the hydrohalic acid salts with the hydrochloride salt being especially preferred. In carrying out the reaction of step (a), the compound of formula II is reacted in equimolar quantities with the acid addition salt of hydroxylamine. In carrying out this reaction, a molar excess of the compound of formula II above or the hydroxylamine hydrochloride salt can be present. Generally, this reaction is carried out in the presence of an organic polar solvent. Any conventional polar solvent can be utilized in carrying out this reaction. The preferred class of polar solvents are the aprotic polar solvents with dimethylformamide, dimethylsulfoxide and hexamethylphosphoramide being especially preferred. In carrying out this reaction, temperature and pressure are not critical and this reaction can be carried out at room temperature and atmospheric pressure. Generally, it is preferred to carry out this reaction at a temperature of from about C. to about 90C.

The compound of formula VI can be converted to the compound of formula I above by treatment with a strong acid or base. This acid or base catalyzed isomerization of the compound of formula VI is carried out with either an alkali metal base or an aqueous inorganic acid. Any conventional alkali metal base such as alkali metal hydroxides or alkali metal lower alkoxides can be utilized in carrying out the reaction of step (b). Generally, the preferred bases are sodium methoxide, sodium hydroxide, etc. However, any conventional alkali metal.

lower alkoxide such as potassium methoxide, etc.; and alkali metal hydroxides, such as lithium hydroxide, potassium hydroxide, etc., can be utilized. In carrying out the reaction of step (b) with an alkali metal base, an inert organic solvent is utilized. Any conventional inert organic solvent can be utilized in carrying out this reaction. Among the preferred inert organic solvents are included, the lower alkanols such as methanol or ethano].

The reaction of step (b) can be carried out by utilizing an acid, preferably an aqueous inorganic acid. Any conventional aqueous inorganic acid can be utilized in carrying out this reaction. Among the preferred aqueous inorganic acids are included the hydrohalic acids such as hydrogen chloride, etc., and sulfuric acid. The

4 reaction of step (b) can be carried out in an inert organic solvent or in an aquoeus medium. If desired, any conventional inert organic solvent can be utilized in carrying out this reaction. Among the preferred inert organic solvents are included, the lower alkanols such as methanol or ethanol. 2

In carrying out the acid or base catalyzed isomerization reaction of step (b), temperature and pressure are not critical. The reaction of step (b) can be carried out at room temperature and atmospheric pressure. On the other hand, elevated or reduced temperatures can be utilized. Generally, this reaction is carried out at a temperature of from 0C. to the reflux temperature of the reaction medium.

In accordance with another embodiment of this invention, malononitrile can be directly prepared from the compound of formula II above by the following reaction scheme: 3

wherein R and R are as above; R is lower alkanoyl; and Y is a mineral acid.

In the first step of this reaction sequence, the compound of formula I is reacted with a compound of the formula VII to produce a compound of the formula VIII. In the salt of the formula VII above, Y can be any proton donating inorganic acid. Among the preferred inorganic acids which are represented by Y in the salt of formula VII are included the hydrohalic acids such as hydrochloric, hydrobromic, etc., and sulfuric acid. In carrying out the reaction of step (c), the compound of formula VII is reacted in equimolar quantities with the compound of formula I. If desired, a molar excess of the compound of formula I or the compound of formula VII can be present in the reaction medium. Generally, this reaction is carried out in the presence of an inert organic solvent. Any conventional inert organic solvent can be utilized in carrying out thisreaction. Among the preferred inert organic solvents are the halogenated hydrocarbon solvents such as chloroform, dichloroethane, methylene chloride, carbon tetrachloride, etc. The reaction of compounds of the formula I with compounds of the formula VII to produce a compound of the fonnula VIII is carried out at a temperature of from 0C. to 30C.

The compound of the formula VIII above is converted to the compound of the formula III (malononitrile) by heating the compound of the formula VIII to a temperature of from C. to the reflux temperature of the reaction medium. The reaction of step (d) is carried out in a conventional inert organic solvent. Any conventional inert organic solvent can be utilized to carry out this reaction. Among the preferred inert organic solvents are the halogenated hydrocarbons such as those mentioned hereinbefore. The solvent which is preferred in carrying out the reaction of step (d) is the same solvent in which the compound of the formula VIII was formed.

In accordance with this invention, the compound of formula III (malononitrile) can be formed directly from the reaction of the compound of formula I with the compound of formula VI] without isolating the intermediate of the formula V111. This is done by first reacting a compound of the formula 1 with a compound of the formula V11 at a temperature of C. to 30C., preferably room temperature, in an inert organic solvent medium and thereafter heating this reaction medium to a temperature of from 70C. to reflux to form the compound of the formula 111. In this manner, a simple and direct means is provided for producing the compound of the formula 111 directly from the compound of formula I.

This invention will be more fully understood from the specific examples which follow. These examples are intended to illustrate the invention and arenot to be construed as limitative thereof. All temperatures are in degrees centigrade.

EXAMPLE 1 Dehydrogenation of dimethylaminopropionitrile to dimethylaminoacrylonitrile The catalytic dehydrogenation of dimethylaminopro- 3.0 mm Hg was collected. This material was 3-dimethylaminoacrylonitrile.

EXAMPLE 3 Preparation of S-Aminoisoxazole To a solution of 40 ml. (37.6 g.) of 3-dimethylaminoacrylonitrile in 200 ml. of dimethylformamide (DMF) was added with stirring at room temperature a solution of g. hydroxylamine hydrochloride in 200 ml. DMF. The resulting mixture was heated for 3 /2 hours at 65-70 and then taken to dryness in high vac- EXAMPLE 4 Preparation of Cyanoacetamide To a solution of 250 mg. of S-aminoisoxazole in 10 In the above reaction, a reaction mixture was prepared containing the catalyst and dimethylaminopropionitrile. Where an ether hydrogen acceptor was utilized, the hydrogen acceptor was present in a molar amount of ten times the moles of dimethylaminopropionitrile in the reaction mixture and the reaction was carried out under nitrogen. In the cases where air was used, the reaction was carried out by exposing the reaction mixture to the atmosphere. The catalyst was present in an amount of about 10% by weight or 30% by weight based upon the weight of the dimethylaminopropionitrile as indicated above. The final product obtained was dimethylaminoacrylonitrile. This product distilled at 1 15C. at 3 mm Hg.

EXAMPLE 2 Preparation of 3-dimethylaminoacrylonitrile 173.0 g. of the diethylacetal of dimethylformamide (1.18 moles) and 400 ml. of acetonitrile were placed in a 1200 ml. autoclave. Air was removed from the autoclave by flushing with nitrogen, and after purging charged to 50 psi. with nitrogen. The reaction was carried out for 36 hours at 150C. Upon completion of the reaction, excess acetonitrile was removed by vacuum distillation using a rotary evaporator at a vacuum of 135 mm Hg. and a waterbath temperature of 60C. maximum. The remaining residue was fractionated using a 24-inch Vigreaux column. After discarding a small first fraction, the material boiling at l 15C. and

ml. methanol was added with stirring a solution of 160 mg. of sodium methoxide in 10 ml. of methanol. The resulting mixture was stirred at room temperature for 15 minutes, then acidified with 4 ml. of 1N hydrochloric acid and evaporated to dryness in vacuo. The residue was dissolved in water and the aqueous solution was extracted with 6 X 50 ml. of chloroform. The combined organic extracts were dried over sodium sulfate and evaporated in vacuo. The residue was crystallized from ethanol/diethyl ether/petroleum ether to yield cyanoacetamide, m.p. 1 121 18; mixture m.p. with an authentic sample 1 12-l 18.

EXAMPLE 5 Preparation of Malononitrile To a solution of 15 m1. of 3-dimethylaminoacrylonitrile in 60 m1. of 1,2-dich1oroethane were added in small portions, 16.5 g. of O-acetylhydroxylamine hydrochloride. After completed addition, the mixture was stirred at room temperature for 20 minutes. Then the solid precipitate of dimethylamine hydrochloride was filtered off leaving a solution containing cyanoacetaldehyde, O-acetyloxime. The filter cake was washed with a small amount of ethylene chloride. The combined filtrates were heated at reflux temperature for minutes. After removal of the solvent under reduced pressure, the liquid residue was fractionated in vacuo. The desired malononitrile distilled at 7180 and l.0l .2 mm Hg.

We claim: I l l. A process for producing a compound of the forv i m r v /NCH=CH CN r v R:

CH-CH I v. V L H v I wherein R, and R are lower alkyl with a hydrohalic or v sulfuric acid addition salt of hydroxylamine in the pres- O ence of an aprotic solvent.

, 2. The process of claim 1 wherein said acid addition comprising the step of reacting at a temperature of salt of hydroxylamine is hydroxylamine hydrochloride.

10C. to 90C, a compound of the formula 

1. A PROCESS FOR PRODUCING A COMPOUND OF THE FORMULA
 2. The process of claim 1 wherein said acid addition salt of hydroxylamine is hydroxylamine hydrochloride. 